Robert K. Brown’s first-person tour through war zones, revolutions, doomed adventures and the rise of Soldier of Fortune magazine has the punch of a Hollywood action thriller. There are heroes, villains, blazing guns, intrigue, humor, swagger and violent death. Unlike an action movie, it’s real. From Cuba to Vietnam, Rhodesia to Latin America and Afghanistan, Bob Brown redefined participative journalism while creating a forum for the global warrior culture.

Each issue of Soldier of Fortune — circulation 1 million plus — is iconic to readers of a special stripe: veterans, active duty, special operators, mercenaries, gun lovers, law enforcement, adventurers, survivalists and those wish they were any of those. It’s not unusual for a combat veteran to admit he got his first glimpse of what he could become in the pages of SOF.

Soldier of Fortune launched in 1975 as a way for Mr. Brown, a Green Beret in Vietnam, to reach out to brothers in arms. SOF became a global touchstone linking a broad community of warriors willing to go anywhere and do anything — for adventure, for a cause or for a price. Along the way, Mr. Brown and his rugged band of paramilitary journalists wrote, photographed and shot their way through a score of revolutions and brush fire wars, were damned and praised by governments around the world, exposed crooks and scam artists and were sued multiple times for enabling mayhem and even murder.

However improbable the success of Soldier of Fortune, the story of its founder and field commander is more so. Bob Brown grew up modestly in Indiana. In the mid-1950s he ended up at the University of Colorado in Boulder, the town that would become home base for SOF. He was idealistic, pugilistic, didn’t much care for authority and had a big case of attitude. He maneuvered through the Army Reserve, became a second lieutenant, shot on the pistol team and, as a part-time student, part-time soldier could barely contain his lust for adventure. The book tells well the twists and turns that led Mr. Brown to Cuba to write about, with sympathy, Fidel Castro’s revolution against the dictator Batista. He didn’t meet Castro, but hung around in the shadows of Havana. When Castro announced he was Communist, Mr. Brown fell in with a scruffy, colorful Florida network of anti-Castro operatives looking to invade Cuba, then Haiti and, for good measure, knock off the dictator of the Dominican Republic. Fortunately for Mr. Brown, those capers fizzled. Back in Boulder, he founded a small publishing company to sell booklets on guerilla warfare.

Recalled to active duty, Capt. Brown went to Vietnam assigned to a Special Forces A Team. He saw plenty of combat, was wounded and managed to exasperate most of the command structure. His commitment to his soldiers and the combat mission was as hard-edged as his disdain for the office-bound careerists, politicians and celebrities he was convinced lost a war that had been won on the ground.

After Vietnam he returned to Boulder, worked odd jobs, wrote a few articles and focused on the growing number and needs of disaffected vets. He played host to a steady stream of warriors looking for the next fight. Legions of combat-hardened American soldiers did not feel welcome at home in the ‘70s, but found a ready market for their skills in the brush fire conflicts that burned on the perimeters of the Cold War.

One of those markets was Africa. In 1974, soldiers of fortune, adventurers and mercenaries (“mercs”) from around the world were headed to Rhodesia to help Ian Smith’s beleaguered white government turn back a communist-backed insurgency. Mr. Brown joined them with his typewriter, camera and gun, committed to telling stories about the fight and the fighters. To make a few bucks, he placed a small classified ad in Shotgun News offering information on becoming a mercenary — and was amazed when hundreds of responses poured in from around the world. The idea was born for Soldier of Fortune magazine.

Journalists for SOF separated the good guys from the bad guys, and their stories were unapologetically anti-communist. SOF became known for tough journalism and breaking stories, calling out the self-promoting but hollow MIA rescue missions led by former Green Beret Bo Gritz, and secured evidence of “yellow rain” chemical attacks being used against Laotians and others. It was a new brand of journalism. As the success of SOF grew, so did the problems of working on the margins of journalism. The classified ads in Soldier of Fortune were lucrative, but those placing them and responding to them sometimes had dark purposes. The magazine was accused of promoting killers for hire. SOF fought back against the lawsuits and was regularly attacked in the mainstream media. Undaunted, Mr. Brown and his teams continued to fan out across the globe, reporting from the thick of combat in every hot spot and hellhole that made headlines — and many that didn’t.

“I Am Solider of Fortune” is a half-century of history told from ground level. The higher value, though, may be in the perspective it offers on the warrior culture. From the outside, it is easy to believe every soldier of fortune, every “private security contractor,” is a Rambo-style wild man, pumped on testosterone. Some of the characters passing through Mr. Brown’s book are that. Others are darkly sinister. Most are measured, disciplined professionals who understand both risk and principle. True, the dialogue in “I Am Soldier of Fortune” often sounds like football coaches arguing in a bar, and SOF brethren are rowdy and don’t play by the rules. So many names and places pop up it’s easy to get lost. However, the strongest characters in his tale share an iron commitment to personal freedom, patriotism, disdain for enemies and a willingness to risk everything. They are tough as nails. Wannabe heroes and me-too patriots don’t fare well under Mr. Brown’s withering prose. Forty years after the Vietnam War, his contempt is fresh for those he believes betrayed American warriors — John Kerry, Jane Fonda and others.

At 80, Robert K. Brown stands as a central figure in a shadow world of secrecy and myth. His book opens that world to readers on the outside. There are many who don’t like Soldier of Fortune magazine and the culture of rogue warrior exploits it represents.